Interpretive Summary: The navel orangeworm (NOW) is a primary pest of almonds and pistachios in California and is controlled in part by destroying unharvested nuts after harvest. Beginning in 2002, a series of studies reevaluating the current tree mummy threshold of 2 nuts per tree as well as the impact of ground mummies and proximity to pistachio orchards on Nonpareil almond kernel damage, were conducted in Kern County. Data from these studies support a more stringent threshold sanitation standard for tree mummies, 0.2 per tree, and also support a ground mummy sanitation threshold of 4 nuts per tree. Proximity to pistachios was an important risk factor for NOW damage greater than or equal to 2%, and this influence extended as far as 3 miles.

Technical Abstract:
The navel orangeworm (NOW) is a primary pest of almonds and pistachios in California and is controlled in part by destroying unharvested nuts after harvest (sanitation), using a sanitation threshold of less than or equal to 2 mummy nuts remaining in the canopy of each tree. Almond and pistachio acreage has increased dramatically throughout the state since the tree mummy threshold was established in the 1980’s and the impact of this expansion in Kern County is unknown. Beginning in 2002, a series of large-scale studies reevaluating the current tree mummy threshold as well as the impact of ground mummies and proximity to pistachio orchards on damage to Nonpareil almond kernels were conducted in Kern County. Data from these studies support a more stringent sanitation threshold for tree mummies, 0.2 per tree, and also support the establishment of a ground mummy sanitation threshold of 4 nuts per tree. Proximity to pistachios was an important risk factor for NOW damage greater than or equal to 2%, and this influence extended to 3 miles from the centroid of the almond research blocks to the margin of the nearest pistachio orchard. In order to meet these sanitation standards in a 100 tree planting, between harvest and sanitation more than 99.6% of the nuts must be collected or destroyed.